Spacer for electron-discharge tubes



March 15, 1949. N. B. KRlM SPACER FOR ELECTRON DISCHARGE TUBES Filed May10, 1945 Inward/ 074 A ar/M723 Z? 5 6217/, A in Patented Mar. 15, 1949SPACER FGR ELECTRON-DISCHARGE TUBES Norman E. Krirn, Newton Highlands,Masa, as-

signor to Raytheon Manufacturing Company, Newton, Mass., a corporationof Delaware application May 10, 1945, Serial No. 593.014

3 Claims.

This invention relates to electron-discharge tubes, and moreparticularly to the means by which the elements of the electrodeassembly are maintained in proper position Within the tube.

Such means for maintaining the electrodes of the electrode assembly inproper position usually comprises one or more spacing members ofinsulating material, preferably of mica, provided with perforationsthrough which said elements extend. As herein used, the termelements isto be understood as including not only electrodes, but also any posts,rods, or the like supporting said electrodes.

It is necessary that said elements have a tight fit in the perforationsthrough which they extend in order to preclude, as much as possible, anydisplacement or vibration of said elements in said perforations, as anysuch displacement or vibrations when the tube is in use will have adisturbing influence that might seriously detract from the satisfactoryperformance of the tube.

In certain tubes, particularly in those of smaller size, such as thoseused in pocket radios, hearing aid devices and the like, said elementsare so small in transverse diameter, and therefore call for such smallperforations in said spacing members, that the insertion of saidelements in said perforations not infrequently requires the use of amagnifying glass by the operator. The operation really requires anexpert operator, and even then the operation is slow and laborious.

It is one of the objects of the present invention to provide meanswhereby the insertion of said elements in the perforations providedtherefor in said spacing members is greatly expedited and facilitatedand can be satisfactorily performed by any operator of ordinary ability.

This and such other aims and objects of the present invention as mayhereinafter appear will be best understood from the followingdescription read in connection with the accompanying drawing of a tubeincorporating one illustrative embodiment of said invention.

In the drawing:

Fig. l is a longitudinal section on line 1-! of Fig. 2, on a materiallyenlarged scale, of a tube incorporating one illustrative embodiment ofthe present invention; and

Fig. 2 is a horizontal cross-section on line 2--2 of Fig. 1 showing atop plan view of the lower spacing member and related parts.

In order to simplify the drawing, the tube selected to illustrate thepresent invention consists of a triode, comprising hermetically sealedenvelope 2 of glass or other suitable material, containing a filamentcathode t, a grid 6 surrounding said filament, and an anode or plate llof generally ellipsoidal shape in cross-section surrounding said grid.Insulating spacing mem bers iii and 52 for the elements of the electrodeassembly are provided, said spacing members each comprising two or moresuperposed insulating plates, preferably of mica. The mica plates beingquite thin, they not infrequently split along a line joining theperforations for the elements to be inserted therein. The use of two ormore superposed plates strengthens said spacing members suificiently toavoid such breakage. Increasing the thickness of said spacing members byusing two or more superposed insulating plates also has the advantage ofincreasing the leakage paths.

For the sake of simplicity each spacing member in the illustrativeembodiment of the invention shown comprises only two such insulatingplate-s l4 and iii. These are preferably provided at their edges with aplurality of suitably spaced toothlilre projections l8 (see 2) whichengage the inner wall of said envelope 2 and brace said spacing memberslaterally.

The filament cathode 4 extends through coaxial apertures 29 and 22provided centrally of said two spacing members H3 and i2, respectively.At one end said filament. cathode d is welded to one end of a resilientelectrically conductive member 26, and at its other end to a stifflead-in conductor and to one of several rivets 28 which serve to clamptogether the two insulating plates i4 and N5 of the lower spacing memberl2, viewing Fig. 1, only two of said rivets being shown, said lead-inconductor 26 being sealed through a press 39 formed at the base of saidenvelope 2. Similar rivets, not shown, may be provided for clampingtogether the plates [4 and 16 of the upper spacing member [0, viewingFig. 1. At its other end said resilient member 24 is welded to one endof a conductor 32, extending through suitable perforations (hereinaftermore fully described) in said spacing members 49 and 2. The other end ofsaid conductor 32 is welded to a leadin conductor 34, scaled throughsaid press 39. Said resilient member 2d keeps the filament cathode undertension and in contact with the edge of the aperture 2!! in the spacingmember I8, the lower portion of said cathode being held in contact withthe edge of the aperture 22 in the spacing member 52 owing to the factthat the rivet 28 to which it is welded is offset from said aperture 22.Ohiectionable vibration of said cathode filament is thus prevented.

The grid 6 is mounted upon electrically conductive posts 38 and 38 whichextend through suitable perforations (hereinafter more fully described)in said spacing members 1!] and i2, one of said posts, the post 3%, forexample, being welded to a lead in conductor ill sealed through saidpress Etll and supporting said grid. The anode or plate 8 is supportedby two electrically conductive posts 42 and 2-4 extending longitudinallyof said plate and Welded to its inner surface in longitudinal channelsformed in the Walls of said plate, one at each end of its major axis,said posts extending through suitable perforation (hereinafter. morefully described) provided'in said two spacing members ill and [2, one ofsaid posts, the post Mi, for example, having its lower end welded to alead-in conductor 46 sealed through said press .iii the upper spacingmember Hi resting upon the upper edge of said plate 8.

In assembling the electrode assembly, the upper spacing member It isslipped down over the upper ends of the elements that are to be spacedthereby, the upper ends of said elements, in the present case, the gridsupporting posts 36 and 33. the anode plate supporting posts 42 and M,and the conductor 32, being threaded through the perforations providedin said spacing member to receive them. In like manner the lower spacingmember 62 is slipped up over the lower ends of said elements, the latterbeing similarly threaded through the perforations provided to receivethem in said lower spacing member I2 in alignment with the correspondingperforations in said upper spacing member Iii.

As stated in the beginning of this specification, one of the objects ofthe present invention is to provide means whereby the heretofore slowand laborious operation of threading said elements through theperforations provided for that purpose in said spacing members may befacilitated and expedited. In the present illustrative embodiment of theinvention, this is accomplished by making the opening through which theelement is inserted in the spacing member sufliciently large to enablethe operator quickly and readily to locate the perforation with the endof said element and insert said element therein. Beyond said largerentrance opening to said perforation the latter is narrowed sufficientlyto cause it closely to embrace the element threaded therethrough andcause it to fit tightly therein and thus firmly to hold it againstdisplacement and vibration.

As shown in the drawing, this result is conveniently' obtained byproviding the plates i l of the two spacing members with perforations 48sufficiently restricted closely to fit the elements inserted therein andhold them securely against displacement and vibration, and making theperforationsv 56 in the plates Hi sufficiently large to enable, them tobe readily and quickly located by theoperator with the point of theelement to be inserted therein, whereupon it is only necessary to pressthe element into the opening when it will be guided automatically intoand through the close fitting perforations 38 in the other plate I4.

If, more than two superposed insulating plates are used to constitute aspacing member, the perforation in the third plate directly superposedupon the second one will exceed the size of the perforation in saidsecond plate by a predetermined, suitable amount, and so on, the size ofthe perforation in each plate exceeding the size of the perforation inthe plate upon which it is directly superposed by a predetermined"suitable amount.

If desired the ends of the elements, such as the grid supporting postsand 38, the plate supporting posts 32 and 44 and the conductor 32, maybe rounded off by any convenient, conventional process. lhis not onlyfacilitates the in sertion of said elements through said perforations c3and 58 but also removes the objectionable burr from the ends of saidelements.

Owingto the fact that for the sake of clearness the tube is shown upon agreatly enlarged scale in the drawing, the angular contour of the innersurface of the perforation 561 in the plate I6 is greatly exaggerated.In actual practice the insulating plates l4 and I6 are extremely thin,they being no thicker than the transverse diameter of the tightlyfitting perforations 48 of the plate I4, so that once inserted in thelarger perforation of plate It, the point of the element glides smoothlyinto the smaller perforation of plate I4.

A getter 52 of any suitable conventional construction is shownconveniently mounted upon a conductor 54 welded to the upper end ofconductor 32.

I am aware that the present invention can be embodied in other specificforms Without departing from the spirit or essential attributes thereof,and I therefore desire the present description to be considered in allrespects as illustrative and not restrictive, reference being had to theappended claims rather than to the aforesaid description to indicate thescope of the invention.

What is claimed is:

1. A spacing member for electrode elements of 2. electronedischargetubes, said spacing membercomprising two superposed insulating plateseach provided with suitably through which to insert electrode elements,corresponding perforations of the two plates being coaxially disposedwhen said two plates are superposed, the size of the perforations in oneof said platesexceeding the size of the corresponding perforations inthe other of said two plates.

2. A spacing member for electrode elements of electron-discharge tubes,said spacing member comprising a first insulating plate and anadditional insulating plate superposed upon said first insulating plate,each of said plates being provided with suitably spaced perforationsthrough which to insert electrode elements, the correspondingperforations of said plates being coaxially disposed when said platesare superposed, the perforations of said first insulating plate being ofa transverse diameter firmly to clamp an electrode element insertedtherein and prevent said element REFERENCES CITED The followingreferences are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date;

1,736,275 Perryman Nov; 19,1929 2,048,257 Glauber July 21-, 19362,087,307 Smith July 20, 1937' 2,188,270 Stahl Jan. 23, 1940 2,256,293Salzberg Sept. 16, 1941 2,350,003 West May 30, 1944 FOREIGN PATENTSNumber Country Date- 676.,3.67 Germany June 2, I939 spaced perforations

